Described herein are toners, and particularly emulsion aggregation toners. The toners exhibit a low melt temperature while simultaneously exhibiting excellent relative humidity sensitivity regarding charging properties. Also described are methods of making such toners.
Advantages of the toners described herein include, for example, the ability to incorporate crystalline materials into the toner to achieve low melting characteristics without sacrificing relative humidity sensitivity.
Low melting, including ultra low melting, toners are known. For example, such toners may be comprised of an amorphous polyester material having a crystalline polyester material mixed therein. The crystalline polyester material imparts the low melting temperature to the polyester toner. An example of such a low melting polyester toner is described in, for example, U.S. Pat. No. 6,830,860, incorporated herein by reference in its entirety.
However, addition of the crystalline polyester material to the amorphous polyester material may cause a lowering of the charging performance of the toner, particularly in higher temperature and/or higher humidity conditions. Thus, the low melting polyester toners may still be improved in terms of relative humidity sensitivity. The affect on relative humidity sensitivity may be because as the toner particles melt, for example during the toner particle formation process, the crystalline polyester material tends to migrate to the toner particle surface, where it crystallizes and may interfere with toner charging in high temperature and/or high humidity conditions.
Attempts to address this potential issue have included placing an additional shell of amorphous polyester material on the toner particle surface, thus covering any crystalline polyester material that may migrate toward the surface. However, it is not an easy procedure to locate the amorphous polyester shell upon the toner particle surface. Moreover, the shell must still be melted during the toner particle formation process, such as during coalescence of the toner particles following aggregation or formation, which again results in the same migration issues as when no shell is included.